Folding implement frame with weight transfer

FIELD

p-0002An implement frame is disclosed and in particular, a frame for an agricultural implement.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0003<figref idrefs="DRAWINGS">FIG. 1</figref> is a top view of an implement frame illustrating a main section and multiple wings;

p-0004<figref idrefs="DRAWINGS">FIG. 2</figref> is a side view of a locking hinge assembly between two of the wings with the hinge assembly in the locked field use position;

p-0005<figref idrefs="DRAWINGS">FIG. 3</figref> is a perspective view of the locking hinge assembly of <figref idrefs="DRAWINGS">FIG. 2</figref>.

p-0006<figref idrefs="DRAWINGS">FIG. 4</figref> is a side view of the locking hinge assembly of <figref idrefs="DRAWINGS">FIG. 2</figref> with the hinge unlocked and in a folded position;

p-0007<figref idrefs="DRAWINGS">FIG. 5</figref> is a rear view of the frame of <figref idrefs="DRAWINGS">FIG. 1</figref> showing the left side in the field use position;

p-0008<figref idrefs="DRAWINGS">FIGS. 6-8</figref> are rear views of the frame, like <figref idrefs="DRAWINGS">FIG. 5</figref>, showing the left side the frame illustrating the folding sequence;

p-0009<figref idrefs="DRAWINGS">FIG. 9</figref> is a rear view of the frame showing the entire frame in the folded transport position;

p-0010<figref idrefs="DRAWINGS">FIG. 10</figref> is a hydraulic schematic of the weight transfer system for frame folding;

p-0011<figref idrefs="DRAWINGS">FIG. 10A</figref> is an alternative hydraulic schematic for the frame weight transfer system;

p-0012<figref idrefs="DRAWINGS">FIG. 11</figref> is a hydraulic schematic of the oil exchange reduction system for reducing the amount of oil exchanged from the tractor when extending the cylinder rods to un-fold the frame;

p-0013<figref idrefs="DRAWINGS">FIG. 12</figref> is a hydraulic schematic of an alternative embodiment of the oil exchange reduction system;

p-0014<figref idrefs="DRAWINGS">FIG. 12A</figref> is a hydraulic schematic of a further alternative embodiment of the oil exchange reduction system;

p-0015<figref idrefs="DRAWINGS">FIG. 13</figref> is a side view of the main frame section illustrating the frame lift wheel assembly in the frame lowered position;

p-0016<figref idrefs="DRAWINGS">FIG. 14</figref> is a side view like <figref idrefs="DRAWINGS">FIG. 13</figref> with the frame in the raised position;

p-0017<figref idrefs="DRAWINGS">FIG. 15</figref> is a perspective view of the main frame section lift wheel assembly illustrating the main frame helper lift cylinder; and

p-0018<figref idrefs="DRAWINGS">FIG. 16</figref> is a hydraulic schematic illustrating of the main frame helper lift cylinder circuit; and

p-0019<figref idrefs="DRAWINGS">FIG. 17</figref> is a hydraulic schematic of an alternative hydraulic circuit for the main frame lift cylinder.

DETAILED DESCRIPTION

p-0020An agricultural implement <b>20</b> is shown in <figref idrefs="DRAWINGS">FIG. 1</figref>. Implement <b>10</b> is an air hoe drill for use with an air cart to plant seeds. However, the present invention can apply to any type of implement and is not limited to an air hoe drill or even to an agricultural implement. The implement <b>10</b> includes a frame <b>22</b> comprising multiple sections as described in greater detail below, a plurality of wheel assemblies and a hitch <b>24</b> to connect the implement to a prime mover such as a tractor to move the implement along the ground in a travel direction shown by the arrow <b>26</b>. Implement <b>20</b> can be directly attached to a tractor or connected behind an air cart that is in turn connected to a tractor.

p-0021The frame <b>22</b> has a main or center section <b>30</b> to which the hitch <b>24</b> is connected. The main section is supported on front and rear main wheel assemblies <b>32</b>. The wheel assemblies are mounted on pivot arms to enable the frame <b>22</b> to be raised and lowered relative to the ground. The frame main section has left and right sides <b>34</b> and <b>36</b> respectively relative to the travel direction.

p-0022A plurality of left and right wings extend from the center section <b>30</b>. Only the right side wings are shown in <figref idrefs="DRAWINGS">FIG. 1</figref> for purposes of clarity. The left side is a mirror image of the right side. The entire frame is shown in <figref idrefs="DRAWINGS">FIGS. 5-9</figref>. Left and right first or inner wings <b>40</b> are pivotally attached to the left and right sides of the main section at inner ends <b>44</b> of the inner wings respectively. Each inner wing is pivotal about a respective inner wing axis <b>46</b> and each inner wing has an outer end <b>48</b>. The inner wings are supported on wing wheel assemblies <b>42</b> adjacent the outer ends <b>48</b> of the inner wings <b>40</b>. Outboard of the inner wings are left and right middle or second wings <b>50</b>. The middle wings <b>50</b> have inner and outer ends <b>54</b> and <b>58</b> respectively and are pivotally attached at the inner ends <b>54</b> to the outer ends <b>48</b> of the inner wings for rotation about middle wing axes <b>56</b>. The middle wings do not have supporting wheel assemblies.

p-0023Outboard of the middle wings are left and right rigid wings <b>70</b>. The rigid wings <b>70</b> have inner ends <b>74</b> and outer ends <b>78</b>. The rigid wings are pivotally coupled to the outer ends of the middle wings for rotation about rigid wing axes <b>76</b>. The rigid wings are supported at the outer ends by wing wheel assemblies <b>72</b>. The rigid wings are coupled to the middle wings by locking hinge assemblies <b>100</b> described in detail below. The locking hinge assemblies hold the rigid wings in place to prevent rotation about the rigid wing axes <b>76</b> when the implement is in the field use position shown in <figref idrefs="DRAWINGS">FIGS. 1 and 5</figref>. The middle and rigid wings act as a single unit with the wing wheel assemblies <b>72</b> supporting both the middle and rigid wings.

p-0024Outboard of the rigid wings are left and right outer wings <b>80</b>. The outer wings have inner and outer ends <b>84</b> and <b>88</b> respectively and are pivotally attached at their inner ends to the outer ends of the rigid wings <b>70</b>. The outer wings rotate about outer wing axes <b>86</b>. Wing wheel assemblies <b>82</b> support the outer wings at the outer ends <b>88</b> thereof.

p-0025The locking hinge assemblies <b>100</b> are described with reference to <figref idrefs="DRAWINGS">FIGS. 2-4</figref>. A pivot joint <b>102</b> couples the rigid wing <b>70</b> to the middle wing <b>50</b> and defines the rigid wing axes <b>76</b>. A guide arm <b>104</b> has one end <b>106</b> coupled to the middle wing at pivot joint <b>108</b>. The other end of the guide arm <b>104</b> is coupled to the rod <b>114</b> of a hydraulic cylinder <b>112</b> by pivot joint <b>110</b>. The cap end of the cylinder <b>112</b> is attached to the middle wing at pivot joint <b>116</b>. A connecting arm <b>120</b> is also attached to the rod <b>114</b> and the guide arm <b>104</b> at the pivot join <b>110</b>. The opposite end <b>122</b> of the connecting arm <b>120</b> is coupled to the rigid wing <b>70</b> at a pivot joint <b>124</b>. As the rod <b>114</b> is retracted, the path of the pivot joint <b>110</b> is controlled by the guide arm <b>104</b>. The connecting arm moves along with the guide arm <b>104</b>. This causes the rigid wing to rotate about the rigid wing axes <b>76</b>, to raise the rigid wing from the field use position shown in <figref idrefs="DRAWINGS">FIGS. 2 and 3</figref> to the folded transport position shown in <figref idrefs="DRAWINGS">FIG. 4</figref>. In the field use position shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, pressure in the cylinder <b>112</b> holds the rigid wing in place with the surface <b>126</b> of the rigid wing firmly butted against the surface <b>128</b> of the middle wing.

p-0026Implement <b>20</b> is shown in <figref idrefs="DRAWINGS">FIGS. 1 and 5</figref> in a field use position in which the main section of the frame and the wings are generally aligned with one another in a horizontal orientation. While shown as being generally horizontal, this is when placed on level ground. The inner wings are allowed a certain amount of rotation about the inner wing axes <b>46</b> to allow the inner wings to follow the ground contours. Likewise, the joined middle and rigid wings are allowed some rotation about the middle wing axes <b>56</b> while the outer wings are allowed to rotate about the outer wings axes <b>86</b>, all to follow the ground contours.

p-0027A plurality of hydraulic cylinders are provided to fold the implement <b>20</b> from the field use position of <figref idrefs="DRAWINGS">FIGS. 1 and 5</figref> to a folded transport position shown in <b>9</b>. The folding sequence is described below. Hydraulic cylinders <b>140</b> are connected to the frame main section <b>30</b> and the inner wings <b>40</b>. The cylinder rods of the cylinders <b>140</b> are coupled to brackets <b>142</b> on the inner wings in a slot <b>144</b>. The slotted connection of the rod to the bracket allows for limited rotation of the inner wings about the inner wing axes as the implement is moved over the ground to enable the implement to follow the ground contours. Similarly, hydraulic cylinders <b>150</b> are connected to the inners wings <b>40</b> and the middle wings <b>50</b>. Hydraulic cylinders <b>180</b> are connected to the rigid wings and the outer wings. Slotted connections of the rods of cylinders <b>150</b> and <b>180</b> allow for limited movement of the wings as described above enabling the wings to follow the ground contours.

p-0028Folding of the implement <b>20</b> from the field use position to the folded transport position is accomplished as follows. First the frame is lowered relative to the wheel assemblies. The fold sequence is then initiated and the frame is raised to its uppermost position. The ground working tools <b>28</b> are then retracted if they are of a retractable design. Folding begins by first actuating cylinders <b>180</b> to rotate the outer wings <b>80</b> about the outer wings axes <b>86</b>. The outer wings are rotated approximately 180 degrees to a position in which the outer wings overlie the rigid wing as shown in <figref idrefs="DRAWINGS">FIG. 6</figref>. The outer wing wheel assemblies <b>82</b> are then retracted relative to the frame, that is, the wheel assemblies are moved to the position relative to the frame they are in when the frame is lowered in the field use position.

p-0029The middle wings <b>50</b> and the rigid wings <b>70</b> are raised together as a fixed unit with the hinge assemblies <b>100</b> still locked. The middle and rigid wings are raised by actuation of the cylinders <b>150</b> and are raised together until the middle wings <b>50</b> are raise to about a twenty degree angle. Before doing so, the cylinders <b>140</b> are retracted to apply a lifting force on the inner wings <b>40</b>. The lifting force is not sufficient to lift the inner wings but to transfer weight from the inner wings to the center section <b>30</b>. This improves stability of the frame during folding and also reduces the load on the inner wing wheel assemblies <b>42</b>. This weight transfer is described in more detail below. After the middle wings are raised twenty degrees, the locking hinges <b>100</b> are released by operation of the cylinders <b>112</b> and the rigid wings are rotated about the axes <b>76</b> about 90 degrees to extend at approximately a right angle relative to the middle wings. The cylinders <b>150</b> are further actuated to rotate the middle wings <b>50</b> a total of approximately 90 degrees about the middle wing axes <b>56</b> to the position shown in <figref idrefs="DRAWINGS">FIG. 8</figref>. Now the middle wings are extending upwardly with the rigid wings extending laterally above the inner wings and with the outer wings between the inner and rigid wings. The rigid wing wheel assemblies <b>72</b> are then retracted relative to the frame.

p-0030The next step in the folding sequence is the actuation of the cylinders <b>140</b> to now rotate the inner wings approximately 90 degrees to the folded transport position shown in <figref idrefs="DRAWINGS">FIG. 9</figref>. The inner wings wheel assemblies <b>42</b> are then retracted. The inner wings are now extending upwardly, the middle wings extend laterally inwardly, the rigid wings extend downwardly and the outer wings extend upwardly beneath the middle wings and between the inner and rigid wings. During the folding operation, the outer wings are rotated a total of approximately 450 degrees from the field use position to the folded transport position. The rigid wings rotate 270 degrees from the field use position to the folded transport position. The middle wings rotate 180 degrees from the field use position to the folded transport position while the inner wings only rotate 90 degrees from the field use position to the folded transport position.

p-0031To fold the implement, the locking hinge joint <b>100</b> is unlocked allowing the rigid wings to rotate relative to the middle wings about the rigid wing axes <b>76</b>. The implement frame <b>22</b> operates as a seven section frame in the field use position and as a nine section frame in the folded transport position. This enables the implement to be folded into a smaller configuration for transport than if it remained a seven section frame. As noted previously, the middle wings do not have wheel assemblies connected thereto. The wing wheel assemblies are only mounted to the wings that are oriented upright in the folded transport position. This helps to minimize the overall height of the implement in the folded transport position as there are no wheel assemblies extending upwardly from the middle wings. Wing wheel assemblies <b>42</b> on the inner wings extend laterally and depending on the size of the tools and wheel assemblies may increase the transport width of the implement <b>30</b> but not the height.

p-0032The implement frame, by having seven section in the field use position and nine sections in the folded transport position enables a frame to be constructed that is greater than 27 meters in width in the field use position but is folded to a transport position that is less than eight meters in width and less than six meters in height. The implement shown has a 96 foot width in the use position and a transport position width of 23 feet and height of 18 feet. This is slightly smaller than the transport dimensions of the 75 foot wide frame disclosed in U.S. Pat. No. 7,497,269. This results in a machine with a significantly greater are covered per pass in the field compared to the machine of the '269 patent without any increase in the transport dimensions.

p-0033A portion of the hydraulic system of the implement <b>20</b> is shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. Due to the number of wings on the implement, when rotating the middle wings <b>50</b> between the folded transport position and the field use position, it is beneficial for stability of the implement and to reduce the load on the inner wing wheel assemblies <b>42</b>, to transfer weight from the inner wings <b>40</b> to the main section <b>30</b>. The weight transfer was mentioned above in connection with the folding of the frame. The weight transfer is accomplished by the hydraulic circuit shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. Hydraulic lines <b>200</b> and <b>202</b> connect to the tractor hydraulic system to delivery oil to the inner wing cylinders <b>140</b> and to the middle wing cylinders <b>150</b>. Valves <b>204</b> and <b>206</b> control the flow of oil to and from the inner wing cylinders <b>140</b>. Valves <b>214</b> and <b>216</b> control the flow of oil to and from the middle wing cylinders <b>150</b>. To unfold the frame <b>22</b> from the folded transport position to the field use position, the inner wing cylinders are extended first by opening the valves <b>204</b>, <b>206</b>. Oil is supplied to the cylinders <b>140</b> by the line <b>200</b> and returned from the cylinder by the line <b>202</b>. This rotates the inner wings about the inner wing axes <b>46</b> from the upright transport position in <figref idrefs="DRAWINGS">FIG. 9</figref> to the generally horizontal use position <figref idrefs="DRAWINGS">FIG. 8</figref>. The valves <b>204</b> and <b>206</b> are then closed. The valves <b>214</b> and <b>216</b> are then opened to extend the middle wing cylinders <b>150</b>. While doing so, oil pressure is delivered through the pressure regulating valve <b>218</b> to the rod end of the inner wing cylinders <b>140</b> while the pilot operated check valve <b>220</b> is opened to allow oil to flow from the cap ends of the inner wing cylinders. This retracts the rods of the inner wing cylinders <b>140</b> to the end of the slots <b>144</b>. The pressure in the cylinders <b>140</b> creates a lifting force on the inner wings but the pressure is regulated by the valve <b>218</b> to not be sufficient to lift the inner wings. This transfers weight from the inner wings to the main section. The added weight on the main section keeps the implement stable during unfolding of the middle wings and reduces the load carried by the inner wing wheel assemblies <b>42</b>.

p-0034<figref idrefs="DRAWINGS">FIG. 10A</figref> shows an alternative hydraulic system for accomplishing the weight transfer. Here, the system is electro-hydraulically controlled with the used of solenoid controlled valves <b>222</b> and <b>224</b> controlling the oil flow back to the inner wing cylinders <b>140</b> for weight transfer.

p-0035Weight transfer to the main section <b>30</b> is also beneficial during the folding operation. This is accomplished by opening all of the valves <b>204</b>, <b>206</b>, <b>214</b>, <b>216</b> and supplying oil through the line <b>202</b> and returning oil through the line <b>200</b>. The cylinder rods are all retracted until they reach the ends of the slots. The pressure in the inner wing cylinders <b>140</b> pulls on the inner wings and transfers weight to the main section. The pressure needed to actually lift the inner wings is greater than the pressure needed to lift the middles wings such that the middle wing cylinders <b>150</b> will continue to retract while the inner wing cylinders held stationary. Once the middle wings are fully rotated, the hydraulic pressure will increase until it is sufficient to retract the rods of the inner wing cylinders <b>140</b> and thereby lift the inner wings. While it is preferred to apply a lifting force on the inner wings for weight transfer without actually lifting the inner wings, it is possible to slightly lift the inner wings before folding the middle wings.

p-0036The need for weight transfer to the main section during folding is due to the large weight being moved when the middle wings are being folded. Weight transfer is not limited to a nine section frame but can be used with other frame configurations as well. The nine section frame, due to its size, has a large weight to be lifted when folding the middle wings. The weight transfer is beneficial. However, weight transfer may still be used with a frame having fewer than nine sections if the frame is sufficiently heavy.

p-0037When extending the rods of the hydraulic cylinders, more oil is introduced in the cap end of the cylinder than is given up from the rod end of the cylinder. The difference in oil volume is the physical volume of the rod itself. With the implement <b>20</b> having many large cylinders to fold the frame, the additional volume of oil going into the cap end of the cylinder than coming out of the rod end to extend all of the cylinders to unfold the implement may exceed the amount of oil available from the tractor hydraulic system reservoir.

p-0038To avoid taking too much oil from the tractor reservoir, the implement hydraulic system includes one or more accumulators <b>250</b> (<figref idrefs="DRAWINGS">FIG. 11</figref>). When the rods are retracted, the accumulators store a portion of the oil coming from the tractor. This results in the amount of oil coming from the tractor being more equal to the amount of oil being returned to the tractor from the cap end of the cylinders, thereby reducing the change in the oil level in the tractor reservoir. Later, when the rods are extended and more oil flows into the cap end of the cylinders than flows from the rod end, the accumulators return oil to the tractor. The oil flow from the rod ends of the cylinders combined with the oil from the accumulators more closely matches the oil flow into the cap end of the cylinders. This again reduces the magnitude of change in the reservoir oil level. The result is that the changes in oil level in the tractor reservoir are within acceptable limits.

p-0039The attached schematic shows the implement hydraulic system. The tractor selective control valves (SCV) <b>252</b> and <b>254</b> control the oil flow in and out of the implement. To retract the rods of the cylinders, shown here as one cylinder <b>256</b>, oil flows in from the tractor SCV <b>252</b>. The oil flow is divided by a mechanical flow divider <b>258</b>. In this embodiment, the divider <b>258</b> is comprised of two gear motors <b>260</b>, <b>262</b> tied together by a shaft <b>264</b>. The displacements of the two motors are fixed and thereby determine the ratio of the oil flow split. For example, the motors may be sized to split the oil flow 85/15. Any desired ratios can be used. In this example, fifteen percent of the oil flows to the accumulator <b>250</b> while eighty five percent flows to the rod end of the cylinder <b>256</b> through the check valve <b>266</b>. The pressure in the line <b>268</b> opens the pilot operated valve <b>270</b> in the line <b>272</b> connected to the cap end of the cylinder <b>256</b>. This allows oil to flow back to the tractor through the SCV <b>254</b> to the tractor reservoir. Since a portion of the oil from the tractor is diverted to the accumulator, more oil is needed to retract the cylinders such that the oil from the tractor is more equal to the oil returned to the tractor then if there was no accumulator.

p-0040To extend the rod, oil flows in through the SCV <b>254</b>. Pressure in the line <b>272</b> opens the pilot operated valve <b>274</b> allowing oil on the rod side of the cylinder to flow back through the flow divider to the tractor. Pilot pressure in the line <b>272</b> opens check valve <b>276</b> thereby allowing oil in the accumulator to also flow back through the divider to the tractor. This produces a more equal flow of oil to and from the tractor so that the net change in the reservoir oil level is within acceptable limits. Other arrangements of the hydraulic system components can be used to accomplish the same function.

p-0041One alternative hydraulic system arrangement is to add dummy cylinders on the implement that operate in the opposite direction so that as the rod of the active cylinder <b>256</b> is retracted, the rod on the dummy cylinder is extended. See <figref idrefs="DRAWINGS">FIG. 12</figref>. There, as the rod of the active cylinder <b>256</b> is retracted, the rod of the dummy cylinder <b>257</b> is extended. In this manner, the dummy cylinder acts as the accumulator with no need for a flow splitter. As one cylinder takes in more oil than it discharges, the other cylinder discharges more oil than it takes in. In such a system, there would be no change in the tractor reservoir oil level if there is a dummy cylinder for each active cylinder. The dummy cylinders must be anchored on each end to structure to ensure they move with the active cylinders and not extend or retract without the appropriate oil pressure. <figref idrefs="DRAWINGS">FIG. 12A</figref> shows an alternative schematic for using dummy cylinders as the reservoir. Here, the dummy cylinder <b>278</b> is vented to atmosphere with the pressure controlled by the pressure regulating valve <b>280</b>. Other types of flow splitters may be used other than the dual motors shown. The above system to reduce the amount of oil exchanged with the tractor is needed as the implement <b>20</b> is intended to be attached to a separate prime mover such as a tractor. This ensures maximum compatibility of the implement with a broad range of tractors. If the frame is part of a self-propelled vehicle, the vehicle hydraulic system would have a reservoir sized to have sufficient capacity to extend all the hydraulic cylinders.

p-0042The wheel assemblies are coupled to their respective frame section by pivot arms rotatably mounted to the main section or wings to enable the frame to be raised and lowered relative to the ground. The pivot arm <b>300</b> is mounted to the main section by a pivot joint <b>302</b> which defines an axis <b>304</b>. The main wheel assembly <b>32</b> is attached to the pivot arm. If the pivot arm <b>300</b> is rotated clockwise as viewed in <figref idrefs="DRAWINGS">FIG. 13</figref>, the main section <b>30</b> of the frame is raised upward. A linkage, not shown, connects the pivot arm <b>300</b> on the front wheel assembly <b>32</b> to the pivot arm <b>303</b> on the rear wheel assembly so that the front and rear of the frame is raised and lowered together. Such linkages are generally known.

p-0043The frame is raised at the end of each pass in a field to turn the implement around. Once turned, the frame is lowered to reengage the tools in the ground. The frame is also raised to support the implement off the ground when transported to and from the field. When raised in the folded transport position, all the weight of the implement is carried by the main wheel assemblies <b>32</b> on the frame main section <b>30</b>. To carry the larger load, the main wheel assemblies <b>32</b> are larger than the wing wheel assemblies. Likewise, the hydraulic cylinders necessary to move the pivot arms <b>300</b> will be larger than the cylinders to pivot the arms carrying the wing wheel assemblies. However, with the larger the cylinder, more oil needs to flow into and out of the cylinder to extend and retract the cylinder rod. Using a large cylinder on the main wheel assemblies will by necessity require longer raise and lower times when making turns at the end of each pass even though in the field use position the weight on the frame main section wheel assemblies is lower. The longer lift and lower cycle time decreases machine productivity. To avoid the increased cycle time, the main wheel assemblies <b>32</b> are provided with two hydraulic cylinders for lifting. One cylinder <b>306</b> is sized to lift the main section when in the field use position and only the weight of the main section needs to be supported by the cylinder <b>306</b>. A second helper cylinder <b>308</b> is provided to increase the load carrying ability to support the load on the main wheel assemblies when the frame is in the folded transport position.

p-0044Cylinder <b>308</b> is connected to the pivot arm <b>300</b> through a swing arm <b>310</b>, pivotally mounted to the pivot arm <b>300</b> by a joint <b>312</b>. The swing arm <b>310</b> allows the pivot arm <b>300</b> to move only by the operation of the cylinder <b>306</b> when desired. However, when it is desired to use both cylinders <b>306</b> and <b>308</b> to raise the frame, the swing arm <b>310</b> bears against the tube <b>314</b> fixed to the pivot arm <b>300</b> to rotate the pivot arm and raise the frame.

p-0045A hydraulic schematic for operating the cylinders <b>306</b> and <b>308</b> is shown in <figref idrefs="DRAWINGS">FIG. 16</figref>. The main valve <b>320</b> opens to extend the rod of main frame cylinder <b>306</b> and the wing cylinders to raise the frame. A second valve <b>322</b> controls the operation of the helper cylinder <b>308</b>. With both valves open, both cylinders are actuated. With only the valve <b>320</b> open, only the valve <b>306</b> is actuated. The valve <b>322</b> is opened when the fold sequence is initiated with the frame in the lowered position. Initiation of frame folding is mentioned above in the description of the fold sequence. Then, when the frame is raised, both cylinders <b>306</b> and <b>308</b> are actuated to lift the frame. This places the swing arm <b>310</b> in contact with the tube <b>314</b> when lifting the frame.

p-0046An alternative arrangement of the “helper lift cylinder” is shown in <figref idrefs="DRAWINGS">FIG. 17</figref>. This arrangement only requires a single hydraulic cylinder <b>354</b> at each of the two front wheel assemblies to raise the main section of the frame <b>30</b>. Oil is supplied and returned through lines <b>350</b>, <b>352</b> connected to a selective control valve (SCV) of the tractor. To extend the rod of lift cylinder <b>354</b>, the valve <b>356</b> is opened, allowing oil to flow from the rod end of the cylinder and oil to flow in the cap end to extend the rod. This is used when lifting the frame for folding. In the field, however, when lifting and lowering the frame for turns, the recirculation valve <b>358</b> is opened and the valve <b>356</b> is closed. This allows oil to flow from the rod end of cylinder <b>354</b> to the cap end when lifting. The only oil needed from the tractor through the line <b>350</b> is the oil for the volume of the rod. Thus, the time needed to lift the frame is reduced as only a small amount of oil is needed. When lowering the frame, valve <b>356</b> remains closed and valve <b>358</b> is opened. Oil flows from the cap end through the valve <b>358</b> to the rod end. The extra oil, (the volume of the rod) is returned to the tractor through the line <b>350</b>.

p-0047While this alternative circuit for reduced raise and lower cycle time is shown with only one lift cylinder <b>354</b>, two smaller cylinders can be arranged in the circuit in parallel in place of one large cylinder. Depending on the particular cylinder sizes, two smaller cylinders may be less expensive than one large cylinder. The cylinders <b>306</b>, <b>308</b> of <figref idrefs="DRAWINGS">FIG. 16</figref> and associated mounting structure constitute a hydraulic actuator assembly. Likewise, the cylinder <b>354</b> of <figref idrefs="DRAWINGS">FIG. 17</figref> constitutes a hydraulic actuator assembly.

p-0048The hydraulic systems, as described above, operate the hydraulic actuator assemblies in first and second modes. In the first mode, the hydraulic actuator assemblies move the pivot arms at a first speed. In the second mode, the hydraulic actuator assemblies move the pivot arms at a second speed. With the embodiment of the hydraulic system as shown in <figref idrefs="DRAWINGS">FIG. 16</figref>, the first mode is with only the valve <b>320</b> open and the cylinder <b>306</b> operating at a faster speed. In the second mode, both the valves <b>320</b> and <b>322</b> are opened and both cylinders <b>306</b>, <b>308</b> are operated at a second, slower speed. With the embodiment of the hydraulic system shown in <figref idrefs="DRAWINGS">FIG. 17</figref>, the first mode with the faster speed is with the valve <b>358</b> open and the valve <b>356</b> closed. The second, slower speed mode is with the valve <b>358</b> closed and the valve <b>356</b> open.

p-0049Having described the implement, it will become apparent that various modifications can be made without departing from the scope as defined in the accompanying claims.